A class of models of biological population and communities with a singular equilibrium at the origin is analyzed; it is shown that these models can possess a dynamical regime of deterministic extinction, which is crucially important from the biological standpoint. This regime corresponds to the presence of a family of homoclinics to the origin, so-called elliptic sector. The complete analysis of possible topological structures in a neighborhood of the origin, as well as asymptotics to orbits tending to this point, is given. An algorithmic approach to analyze system behavior with parameter changes is presented. The developed methods and algorithm are applied to existing mathematical models of biological systems. In particular, we analyze a model of anticancer treatment with oncolytic viruses, a parasite-host interaction model, and a model of Chagas' disease.
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http://dx.doi.org/10.1016/j.mbs.2006.10.006 | DOI Listing |
Int J Pharm
January 2025
Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Hydrophobicity is associated with drug transport across membranes and is expressed as the partition coefficient log P for neutral drugs and the distribution coefficient log D for acidic and basic drugs. The log P and log D predictions are deductively (or with artificial intelligence) estimated as the sum of the partial contributions of the scaffold and substituents of a single molecule and are used widely and affirmatively. However, their predictions have not always been comprehensively accurate beyond scaffold differences.
View Article and Find Full Text PDFSci Rep
December 2024
School of Vehicle and Energy, Yanshan University, 438 West Hebei Avenue, Qinhuangdao, 066004, People's Republic of China.
This study presents a strategy for an intelligent vehicle trajectory tracking system that employs an adaptive robust non-singular fast terminal sliding mode control (ARNFTSMC) approach to address the challenges of uncertain nonlinear dynamics. Initially, a path tracking error system based on mapping error is established, along with a speed tracking error system. Subsequently, a novel ARNFTSMC strategy is introduced to tackle the uncertainties and external perturbations encountered during actual vehicle operation.
View Article and Find Full Text PDFNanophotonics
May 2024
Institute of Fundamental Physics (IFF), Consejo Superior de Investigaciones Cientificas (CSIC), Madrid, Spain.
Spontaneous emission is one of the most fundamental out-of-equilibrium processes in which an excited quantum emitter relaxes to the ground state due to quantum fluctuations. In this process, a photon is emitted that can interact with other nearby emitters and establish quantum correlations between them, e.g.
View Article and Find Full Text PDFJ Chem Phys
November 2024
School of Mathematics, Monash University, Clayton, Victoria 3800, Australia.
Enzyme-catalyzed reactions involve two distinct timescales: a short timescale on which enzymes bind to substrate molecules to produce bound complexes and a comparatively long timescale on which the molecules of the complex are transformed into products. The uptake of the substrate in these reactions is the rate at which the product is made on the long timescale. Models often only consider the uptake to reduce the number of chemical species that need to be modeled and to avoid explicitly treating multiple timescales.
View Article and Find Full Text PDFCogn Neurodyn
April 2024
Department of Mathematics and Information Science, Henan University of Economics and Law, Zhengzhou, 450046 China.
Multiple delays and connection topology are the key parameters for the realistic modeling of networks. This paper discusses the influences of time delays and connection weight on multi-delay artificial neural models with inertial couplings. Firstly, sufficient conditions of some singularities involving static bifurcation, Hopf bifurcation, and pitchfork-Hopf bifurcation are presented by analyzing the transcendental characteristic equation.
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